Controllable pitch propeller



July 19, 1938. E PALME'R AL 2,124,078

CONTROLLABLE PITCH PROPELLER Filed April 14. 1936 5 Sheets-Sheet 1 IN VEN TOR).

PICHARD E. PALMER and CHARLEs 5.J.M\=NEIL JR.

'- ATTO" s.

July 19, 1938. R. E. PALMER ET AL CONTROLLABLE PITCH PROPELLER Filed April 14, 1936 5 Sheets-Sheet 2 INVENTORS QICHAQD E. PALMER CHARLES $.J-MMNEKLJR.

ATTORN S.

July 19, 1938. R. E. PALMER ET AL CONTROLLABLE PITCH PROPELLER Filed April 14, 1936 5 Sheets-Sheet I5 INVENTOR5. QICHAIED EPALMER. CHARLES S.J.Mx-NEIL JR. BY 1 A TTO q" YS.

July l9, 1938. R. E. PALMER ET AL 2,124,078

CONTROLLABLE PI TCH PROPELLER Filed April 14. 1936 5 Sheets-Sheet 4 [LL m n z {I INVENTORS. QIcHAQD E PALMER CHARLES smmmem J2.

BY -I l July 19, 1938.

R. E. PALMER ET AL CONTROLLABLE PITCH PROPELLER Filed April 14, 1936 5 Sheets-Sheet 5 T. mm WM U i Q F M a QM W Vm\ 5 a g 4 iHHUn Q Z MJHHWHHHW 7 Hw 9 4 9 4 4 g 3 CHQLE3 SJflAcNElL JR.

Patented July 19, 1938 CONTROLLABLE PITCH PROPELLER Application April 14, 1936, Serial No. 74,276

4 Claims. (Cl. 170-163) UNITED STATES PATENT OFFICE This invention relates to controllable pitch aeronautical propellers.

Objects of the invention are to provide a propeller hub organization having an improved planetary speed reducer between a relatively high speed electric motor carried by the hub, and the propeller blades; to provide an improved bearing organization for supporting the blade in the hub against centrifugal and centripetal forces; to provide means for permitting movement of the blades between defined pitch limits, said means comprising switches to break the electric motor circuit responsive in their action to propeller blade movement; to provide a composite structural organization in which the several mechanisms are compactly disposed to facilitate maintenance and to render fabricating and assembly processes easy, and to provide essential components in a propeller of the character mentioned which correlates to produce an eflicient mechanism.

' speed reducer;

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. 4 is an enlarged section through the speed reducer showing the gear relationships;

Fig. 5 is an enlarged section on the line 5-5 of Fig. 4;

Fig. 6 is a section through the propeller hub showing details of the limit switch;

Fig. '7 is a section on the line '|l of Fig. 6;

Fig. 8 is a section on the line 8-8 of Fig. 7;

Fig. 9 is a section on the line 9-9 of Fig. 8; and

Fig. 10 is a section on the line Ill-40 of Fig. '7.

Referring first to Fig. 1, there is shown a propeller hub it having a plurality of. blade sockets l2 each having a cylindrical bore l3 within which a ball bearing i5 is inserted, the outer race of the latter resting a socket shoulder l4. This bearin s, as s apparent in the drawings, arranged foi nning radial loads due to propeller blade thrust, and axial, inwardly directed loads. A propeller blade 46 is encircled by the bearing l5, and a plurality of ball bearings I! are stacked on the bearing 55 to assume radial and outwardly directed, or centrifugal loads. It will be noted that the outer races of the bearing l5 and the innermost bearing ll are separated by a clearance IE, to prevent abutment of the races when the blade holding nut l 9 is screwed Within the socket to bear upon the outer race of the top bearing I1. By screwing in this nut, the several ball bearings are pre-loaded by which the outer race of the bottom bearing I1 is pressed toward the outer race of the bearing l5, thus positively establishing the positions of the bearings to prevent either inward or outward movement of the blade IS in its socket l2, while allowing free turning of. the blade. When the propeller is in operation, centrifugal blade forces tend to force the blade out of the socket, whereby the inner and outer races of the bearings I! are jammed against the blade and socket, producing a substantial irictional engagement between races and surfaces by which each bearing of the stack assumes a proportional share of the centrifugal load. This frictional engagement prevents all of the centrifugal load being assumed by the outermost bearing I! and the nut l9.

By this bearing arrangement, effective piloting of the blade in its socket accrues, the blade being positively held in perfect alinement. A maximum of resistance to bending stress in the blade is afforded, by having the relatively large diameter ball bearings and by the relatively great distance between the outermost and innermost ball bearings.

A locking lug is arranged for holding the nut [9 in place, Vernier slots 2| and 22 being formed in the nut I9 and blade socket I2, respectively, to receive the lug.

The inner end of the blade I6 is provided with a combined abutment and bevel gear sector 23, which may be integral with the blade, or may be rigidly attached thereto by screw threads and a pin 23', as shown. The bevel gear sector 23 is drivably engaged with a bevel gear 24 coaxial with the propeller hub, this gear 24 being the driven element of a speed reducer 25 coaxial with, and mounted ahead of the hub H in a housing 26. An electric motor 21 is mounted on the housing 26, ahead thereof and coaxial therewith, and serves to drive the speed reducer.

The speed reducer is shown in detail in Figs. 2 to 5 and comprises what might be termed a differential planetary gear train. The motor shaft 28 carries a driving pinion 29, which is meshed with a plurality of planet pinions 30 borne in a planet carrier 3| carried on bearings 32 in the housing 26. Encircling the carrier 3| is an internal gear 33, fixed in the housing 26. Tandem planet pinions 34 are integral with the pinions 30, and therefore revolve at the same speed as the pinions 30. A driven internal gear encircles and engages the pinions 34, and is driven thereby. By referring to Fig. 5, it will be seen that the pitch circle diameters of the gears 33 and 35 are only very slightly different, the difference (in radius) being designated at 36. In the present embodiment, wherein a speed reduction of 1 to 25,000, or thereabouts, is desired, the diameter differential, represented by 36, is very small, and gear teeth of appropriate pitch are chosen to eifect proper meshing between pinions 30 and gear 33, on the one hand, and pinions 34 and gear 35 on the other hand. It will be apparent that a very high speed reduction flows from this arrangement; since the gear 33 is stationary, gear 35 will creep relative thereto at a rate determined by the proportion of the dimension 36 to the pitch radius of the gear 33 through the functioning of the planet pinions, which in turn are driven at reduced speed by the pinion 29. The driven internal gear 35 is attached to the blade driving bevel gear 24.

In the type of propeller described in Patent No. 1,951,320, issued to W. J. Blanchard, a somewhat similar blade pitch changing organization is described, using, however, a heliocentric speed reducer. The planetary speed reducer here described has been found to be much more eflicient, since the gears transmit their driving effort by gear tooth contact, rather than by sliding pin contact which obtains in the heliocentric reducer. Previously, to provide gear trains to eifect speed ratio changes on the order of 25,000, a multiplicity of epicyclic or ordinary gears, or a series of worm reductions have been deemed necessary which are obviated by this mechanism.

The electric motor used in the propeller herein shown is reversible, and is preferably reversible by having forward" and reverse" field windings which are connected to a selector switch in the aircraft through suitable slip rings and brushes between the propeller hub and power plant. To prevent an operator from effecting propeller blade pitch changes beyond the proper operating range of pitch, means are provided to open the motor circuit when the blade has been moved by the motor to the limit position. This organization is shown in Figs. 6 to 9 and comprises cam rings 40 and 4| carried -by the driven shaft portion 42 of the speed reducer 25. This shaft rotates the propeller blades for pitch change thereof. The lobe on the cam ring 4| engages a cam follower 43 comprising a. bellcrank pivoted at 44 to the housing 26, the lower end 45 of the bellcrank being bifurcated to embrace a switch terminal 41 adapted to make electrical contact with a button terminal 49 mounted in the hub I the terminals 41 and 49 being guided axially by a sleeve 48. Figs. 8 and 9 show the cam 4| operating the cam follower to open the switch after the propeller has been adjusted to the limiting high pitch position. The cam 40 operates on a cam follower, bellcrank and switch, similar to those described, to control the low pitch limit of blade position. This low pitch switch is always closed except when the cam opens it in response to movement of the propeller blades to the low pitch limit. Thus, either one of the high pitch or low pitch limit switches are always closed, so that, should the high pitch limit switch have been opened, the low pitch circuit is in readiness to operate the motor.

The speed reducer 25 and the motor 21 are unitary with the housing 25, the latter having attached thereto a flange plate 5| by screws 62; the plate serving as a carrier for the gear 24 and also serving as a mounting for a de-icing spinner which may embrace the whole power unit. The whole unit, with the plate 5|, is attached to the hub II by screws 52 shown in Figs. 7 and 10. The number 53 inFlg. 6 represents the mounting plane of the power unit to the hub. A spline connection 54 serves as a separable driving connection between the elements 24 and 42 when the unit is removed, and the electrical terminals 41 and 49 respectively stay with the power unit and hub upon power unit removal, the bellcranks 45 likewise staying with the power unit upon removal of the latter; It will be noted that the terminals 41 and 49 are close to the mounting plane 53, so that coincidental registry of these terminals occurs when the power unit is assembled to the hub, the terminals being ready for contact in accordance with the positions of the cams 40 and 4|.

While we have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. We aim in the appended claims to cover all such modifications and changes.

What is claimed is:

1. In a controllable pitch propeller comprising a hub, blades rotatably mounted in the hub for pitch change, an electrically energized power unit consisting of a motor and a speed reducer, said unit being detachably mounted in coaxial relation with the propeller hub, conductors for the motor carried within the power unit and having terminals substantially at the mounting plane of the power unit, cooperating terminals carried by the propeller hub adapted to match with the respective power unit terminals when the power unit is in assembled relation on the hub, and blade pitch limiting switch means operated by the power unit for moving said terminals into and out of contact with each other. I

2. In a controllable pitch propeller comprising a hub, blades rotatably mounted in the hub for pitch change, an electrically energized power unit consisting of a motor and a speed reducer, said unit being detachably mounted in coaxial relation with the propeller hub, conductors for the motor carried within the power unit and having terminals substantially at the mounting plane of the power unit, cooperating terminals carried by the propeller hub adapted to match with the respective power unit terminals when the power unit is in assembled relation on the hub, and blade pitch limiting switch means operated by the power unit for moving said terminals into and out of contact with each other, said limiting means being mounted in and being removable with said power unit upon detachment thereof from the propeller.

3. In a controllable pitch propeller, a hub, a unitary electric power unit having an attaching face in fitting engagement with said hub, means for attaching said unit to said hub, blade pitch control switches electrically connected with said unit and carried thereby, electrical cn bles in said hub having terminals adjacent to the attaching face. and elements of said switches carried by and movable relative to said unit, movable into and out of contact with said terminals during propeller operation, said switches and elements being bodily removable from said propeller hub and separable from said terminals as part of said unit.

4. In a controllable pitch propeller, a hub having a mounting face, electrical cables carried in said hub having contact terminals at said mounting face; an electric motor power unit having a mounting face for fitting engagement with said hub mounting face, switch elements movable with and relative to said unit, connected with said motor, having contact points contactable with said terminals upon switch actuation when said unit is assembled on said hub, said contacts and elements being so disposed on respective mounting faces as to be in position for operative contact upon assembly of said unit upon said hub.

RICHARD E. PALMER. CHARLES S. J. MACNEIL, JR. 

